请帮我看一下这英文句子写得对吗?谢谢.If you change background color from red to green, then you could not be changed back to red.中文背景：哪果你将背京色从红色变成绿色,那你就不能再变回红色了.

...then it cannot be change back to red.

if you change the background color from red to green, you may not be able to change it back.

If you've changed the background color from red to green,you won't change it back then.

有个小错误，应该是If you change background color from red to green, then it could not be changed back to red

If you change the background color from red to green, then you could not chang it back .If you change the background color from red to green, then it could not be changed back .

If you change the red backgroud colour to green, then it can not be red again.